Washington, DC has the National Mall’s monuments and Smithsonian museums, and around them rowhouse neighborhoods, waterfront districts and government offices. Pick a hotel by its Metro line and the part of the city you will spend the most time in.
The National Mall runs from the Capitol toward the Lincoln Memorial, with Smithsonian museums along the way. It is a long walk from one end to the other. From a Penn Quarter or Downtown hotel you can walk to museums, the White House and Capital One Arena, and several Metro lines stop nearby.
Capitol Hill has the Library of Congress, the Supreme Court and Eastern Market, set among residential streets. If you arrive on Amtrak, Union Station is right there. North of Downtown, Dupont Circle, Logan Circle and Shaw have the restaurants and galleries, and more going on in the evening, away from the Mall.
Georgetown has historic streets, the C&O Canal and a Potomac waterfront, but no Metrorail station. Foggy Bottom has one, and it is close to the Kennedy Center and George Washington University. South of the Mall, the Wharf has waterfront restaurants and concert venues. Navy Yard is near Nationals Park.
Spring brings cherry blossoms around the Tidal Basin, and autumn is good weather for walking between the museums and monuments. Summer afternoons are hot and humid, so start outdoor visits early. Metro runs to Reagan National and Dulles airports. If you drive, ask what the hotel charges for its garage and how you get in.